#include <reg51.h>
#include <intrins.h>

unsigned char x, y, i, w, digit, j = 0;
char mas[10];
float numb, m = 0;
//char scancode[] = {0x7f,0xbf,0xff};

Delay(int t)
{
  while(t--);
}

char what(void); 

scan() interrupt 2
{
  w=P2;
  j++;
  if(j == 3) 
    j = 0;
  P3=w;
  Delay(100);
  what();
  Delay(100);
}

main ()
{
  x = 0xFE;
  numb = 0;
  i = 0;
  m = 0;
  IT1 = 1;
  EX1 = 1;
  EA = 1;
  while (digit != 'e')  Delay(100);
  while(1);

}
char what(void)
{
  if(i == 0) // clear all
  {
    numb = 0;
    m = 0;
  }

  switch (w) // check value of button
  {
    case 0x7d: digit='.'; break;
    case 0x7b: digit='.'; break;
    case 0x77: digit='9'; break;
    case 0x6f: digit='8'; break;

    case 0xbd: digit='7'; break;
    case 0xbb: digit='6'; break;
    case 0xb7: digit='5'; break;
    case 0xaf: digit='4'; break;

    case 0xdd: digit='3'; break;
    case 0xdb: digit='2'; break;
    case 0xd7: digit='1'; break;
    case 0xcf: digit='0'; break;

    case 0xed: digit='e'; break;
    case 0xeb: digit='.'; break;
    case 0xe7: digit=','; break;
    case 0xdf: digit='-'; break;

    default: digit=0xff;
  }

  if(digit == 0xff) // exit if default
  {
    goto exit;
  }

  if(digit == ',') // if , is readed
  {
    m = 1; // need to divide
    mas[i++] = digit; // write , to massive
    goto exit;
  }

  if(digit == 'e') // if end
  {
    if(m)
    {
      numb = numb / m; //divide
    }
    i = 0; // clear all
    m = 0;
    goto exit; //and exit
  }
  else // in other cases
  {
    mas[i++] = digit; // write digit to massive
    if (mas[i - 1] != '-') // if digit
    {

      numb = numb * 10 + (digit & 0xf);
      if (i == 2 && mas[0] == '-') // if negative
      {
        numb = -numb; // negative
      }

      if (m) // id we divide
      {
        m *= 10; // numbers after
      }
    }
  }
exit:
  return digit;
}